add kyeword polymer.
Merge pull request #317 from qilicun/kw_polymer

add kyeword polymer.
size of PLYMAX should be determined by NPLMIX in REGDIMS not MISCIBLE.
Let parser recongnize keyword WPOLYMER.
Merge pull request #318 from qilicun/fix_ply_kw

size of PLYMAX should be determined by NPLMIX in REGDIMS not MISCIBLE.
Merge pull request #319 from qilicun/add_wpolymer

Let parser recongnize keyword WPOLYMER.
JSON keyword definitions: add a "sections" item

this which specifies the allowed sections of the keyword. (surprise!)
ParserKeyword: add the glue code so that it knows its sections
JSON keyword definitions: make the "sections" item mandatory

the empty list can be used which means that the keyword may occur in
any section. (which is useful for e.g. section delimiters.)
Extend deck grooming functions to detect keywords which are in invalid sections