Refactor pre-commit into separate function files

[TurtleEngr]

Refactor pre-commit to include functions from files in ~/.pre-commit.d/ and/or PROJ/.pre-commit.d/ The functions can get their options from "git config" variables. The PROJ/.pre-commit.d/ and files would be versioned, so the PROJ/.git/hooks/pre-commit can always call them.

For example:

.pre-commit.d/
    CheckFileNames
    CheckWhiteSpace
    CheckForTabs
    CheckNotRaw
    CheckBigFiles