[core.logger] fix minor typos
[core.logger] allow to disable colors in ColoredFormatter

Up to now this could only be toggled globally.
[core.logger] allow for simultaneous stream and file logging

If the user sets pymor.core.logger.FILENAME, each logger obtained by
getLogger() will additionally log to this specified file. This can be used
to create a log file that should be very close to the output created on the
console, e.g. by:

    from tempfile import NamedTemporaryFile
    import pymor.core
    tmp_filename = NamedTemporaryFile(delete=False).name
    pymor.core.logger.FILENAME = tmp_filename
[operators.basic] add sanity check to apply_inverse of NumpyMatrixOperator
Merge branch 'master' into blocks
Merge branch 'sanity_checks' into blocks
[reductors.block] update doc of GenericBlockRBReconstructor
[reductors.block] add first draft of restricted_to_subbasis (untested)