Adds pattern matching filter.
Adds tests for pattern matching filter.
Adds literal syntax to filter.
Adds tests for literal fitler syntax.
Adds docs on pattern matching filter.
Merge branch 'next' into merge_br
Merge branch 'next' into sam_1328 (nested filter_call changes)

Conflicts:
	src/rdb_protocol/func.cc
	src/rdb_protocol/terms/seq.cc