Improve mega selection in randoms

Megas now have their own viable moves, so that more unique megas like Heracross, Charizard and Mewtwo can have their viable options.

Potential mega evolving candidates can now be selected without their mega stone.  For example, if the team has Gengar with Gengarite, Heracross without Heracronite can be added.

Make multiple mega evolution selection random

It mistakenly always picked the Y forme rather than randomly choosing either.

Reduce number of getTemplate() calls

Slayer95 pointed out that this is a better implementation.

Fix syntax error

Improve randoms mega selection

Simplifying the code by having the mega template stored in 'template'.  For abilities, the original template is stored in 'baseTemplate'.  Also added the improved mega selection for Random Doubles, which would be affected by giving viable moves to megas in formats-data.js.

Improve mega selection in randoms

Megas now have their own viable moves, so that more unique megas like
Heracross, Charizard and Mewtwo can have their viable options.  Potential
mega evolving candidates can now be selected without their mega stone.
For example, if the team has Gengar with Gengarite, Heracross without
Heracronite can be added.
Merge pull request #1034 from Relados/master

Improve mega selection in randoms