Small reaction library for silicon hydrides.

This is a very small set of reactions found in Giunta et al., 1990, J.
Appl. Phys. They are all high pressure rates in Arrhenius format and come
from a few different sources.
Started a thermo library for silicon hydrides.

Values come from the NIST webbook.
Merge branch 'silicon-hydrides' of https://github.com/bslakman/RMG-database into silicon-hydrides

Conflicts:
	input/kinetics/libraries/Silicon_Giunta_1990/dictionary.txt
	input/kinetics/libraries/Silicon_Giunta_1990/reactions.py
Added some silicon H-Abs groups.

Updated group definition and tree for silane