Adding LICENSE file to project

[kshithijiyer]

No description provided.

[pjdarton]

If we're going to have a license file, it should be 100% consistent with the license texts elsewhere in the plugin.
I've done a quick trawl through the code and, while a lot of files don't mention a license at all, those that do reference Apache 2.0 ... but use a much shorter form than this file.
e.g. vSphereCloudSlaveTemplate says:

 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.

I'm not a lawyer, but I think that's sufficient - it's saying where the full text can be obtained, and so we don't need to include it all in this file; we can just reference the official license just like we do everywhere else.

We especially do not need, and should not include, the text that's at the end of this file that explains how to apply the license to the code.

Lastly, I'm not 100% sure of the legalities of adding a license file to "someone else's code".
While it's probably the case that everyone who's contributed wouldn't object, there's 19 .java files and 14 .jelly files without any license information, and so it might not be legal to specify a software license on code that "someone else" wrote, however well-intentioned such a statement might be.
I'm not a lawyer so I'm not sure. If you are a lawyer then please tell me why this is ok...

[pjdarton]

I've been looking into this some more and I don't believe that this file is entirely necessary.
The pom.xml file specifies the Apache 2.0 license applies to the plugin code overall (and this is what Jenkins reports in the plugins pages).
There's no need to copy/paste the full license text here as that just adds data-duplication.

If you want to make it more obvious for people what the license is, I'd suggest adding a LICENSE file which simply instructs readers to look in the pom.xml file, as that's where the definitive statement is.

[pjdarton]

This has been an interesting PR that provoked some investigations into unfamiliar (for me at least) territory. However, we've come out of it stronger...

Because of the questions this raised, I pinged my friendly lawyer contact and they "suggested" that we really ought to make it very clear (a) what the license was and (b) that any contributions to this code had to also be made under the same license.
So, I did.
As this PR hadn't been updated to include the truncated LICENSE file I requested, I couldn't use this PR for the basis of all that work, so I created #109 instead.

I believe that #109 addresses all the concerns that prompted this one, and goes beyond that to make it abundantly clear precisely what software license this code may be used under ... as well as providing some (long overdue!) suggestions about how best to go about contributing.

So, thanks for the PR - it certainly pushed things forward - but it's now been overtaken by the changes it prompted and is now obsolete.