better nested container support in abigen

[taokayan]

as https://github.com/lonkly mentioned in #187

optional <vector < string > > does not work as well

I think the better way is to make a matrix to describe, test & fix each combination of nested containers:
for example:
list of supported containers:
vector, set, optional, map, pair, tuple:

list of possible nested combinations and their current status:

	vector/set	optional	map	pair	tuple
vector/set	not supported	not supported	not supported	not supported	not supported
optional	not supported	not supported	not supported	not supported	not supported
map	supported	supported	supported	supported	supported
pair	supported	supported	supported	supported	supported
tuple	supported	supported	supported	supported	supported

We will need to add more supports in the future

[bogniq]

Is the above list of nested combinations up to date? It says map-nested-in-map is supported, but I tested using the current develop branch (see attachment) for #1042, and the ABI misses the definition of a map with another map as value.
(One workaround is to use typedef or using for the nested map, as suggested by #658 (comment).)
map_nest.cpp.txt
map_nest.abi.txt