Bugfix: DataChangeListener must always store the maximum modification flag inside webglData.

Problem:
1. Value Size Changed
2. Value Value Changed
3. Rendering / Buffer Update
During the buffer update, the renderer assumes that only the value changed.
Thus, only the value gets updated to a buffer of incorrect size.
Xflow bugfixes.
Xflow change: Empty buffers are now always returned as 'null'.

Thus, for the result there is no difference between no buffer defined and empty buffer.
Added error message for attemp of render mesh without any vertex attributes (due to empty buffers).
Added extra check for empty position attribute of mesh.
Added several README.md files throughout the repo for documentation.
Added build instructions / documentation.
Rather link to the src folder contain README.md instead of linking to the README.md directly
Fixed some encoding issued in root README.md
Added src folder documentation (overview)
Fixed spelling errors.
Added xflow folder documentation
Fixed reference
Added documentation for the test suit
Added documentation to Xflow interface structures.
Removed unused code in Xflow.
Removed rendermesh file from build system.
Merge branch 'documentation' into develop
Added annotations to pager
Extended program to support sampler2D[]