replaced gram-schmidt by modified-gram-schmidt

Conflicts:

	src/pymor/la/gram_schmidt.py
[defaults] more sensible defaults for gram_schmidt_tol and bicgstab_tol
[la.gram_schmidt] improve logging
[la.gram_schmidt] refactor main loop
[la.gram_schmidt] do not orthogonalize wrt. removed vectors
[la.gram_schmidt] make reorthonormalization configurable
[la.gram_schmidt] move numpy_gram_schmidt and numpy_gram_schmidt_basis_extension to playground
[la.gram_schmidt] make find_duplicates configurable
[la.gram_schmidt] add attribution
[la.gram_schmidt] begin log messages uppercase
[demos] display gram_schmidt log messages in thermalblock demo
[la.gram_schmidt] small tweaks
Merge branch 'gram_schmidt'