More docs added
Fixed #185: a bug in multiplying two matrices containing vectors (worked fine for arrays)
Output of matrix multiplication is now consistently squeezed
More docs added
Added LaTeX conversion of expressions using toTex() on expression.
Also added some basic tests, which cover some use cases; but should be expanded.
Changed boolean true and false symbols
Allow using symbols in subscript.
Test failed because of missing check of parameter type.
Some tweaks and fixes
Merge branch 'feature/106-LaTeX-toTex' into develop

Conflicts:
	lib/expression/node/AssignmentNode.js
	lib/expression/node/ConstantNode.js
	lib/expression/node/OperatorNode.js
	lib/util/latex.js