Expose API to check whether the Siddhi App is stateful or not #1373

[suhothayan]

Purpose

This exposes queries, partitions, windows, triggers, and tables to check whether they are stateful or not.
Also add more test cases that are missed before.
Fixes #1373

[pcnfernando]

I'm checking the Travis failure.

[codecov-io]

Codecov Report

Merging #1413 into master will increase coverage by 1.42%.
The diff coverage is 68.6%.

@@             Coverage Diff              @@
##             master    #1413      +/-   ##
============================================
+ Coverage     65.31%   66.73%   +1.42%     
  Complexity       37       37              
============================================
  Files           632      633       +1     
  Lines         26662    26688      +26     
  Branches       4214     4214              
============================================
+ Hits          17414    17810     +396     
+ Misses         7795     7401     -394     
- Partials       1453     1477      +24

Impacted Files	Coverage Δ	Complexity Δ
...core/src/main/java/io/siddhi/core/table/Table.java	28.01% <ø> (ø)	0 <0> (ø)	⬇️
...ore/util/parser/helper/DefinitionParserHelper.java	74.42% <ø> (ø)	0 <0> (ø)	⬇️
...n/java/io/siddhi/core/stream/output/sink/Sink.java	72.18% <0%> (-0.55%)	0 <0> (ø)
...ava/io/siddhi/core/stream/input/source/Source.java	82.35% <0%> (-1.23%)	0 <0> (ø)
...va/io/siddhi/core/util/parser/SiddhiAppParser.java	78.27% <100%> (+0.08%)	0 <0> (ø)	⬇️
...siddhi/core/partition/PartitionStreamReceiver.java	77.04% <100%> (ø)	0 <0> (ø)	⬇️
...n/java/io/siddhi/core/util/parser/QueryParser.java	94.59% <100%> (ø)	0 <0> (ø)	⬇️
...re/src/main/java/io/siddhi/core/window/Window.java	76.36% <100%> (+0.21%)	0 <0> (ø)	⬇️
.../main/java/io/siddhi/core/table/InMemoryTable.java	98.64% <100%> (+6.86%)	0 <0> (ø)	⬇️
...uery/processor/stream/AbstractStreamProcessor.java	97.91% <100%> (+0.04%)	0 <0> (ø)	⬇️
... and 35 more

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[pcnfernando]

Travis failed due to an intermittent test failure.