Per-project config file

[julianhyde]

CLC should look for a config file in the root directory of a project (compare how.travis.yml is used by Travis CI).

Projects should be able to add or remove words and phrases.

For example, I have an issue with flagging 'dummy value'. I know the origin of the word. But it is a term of art, there is no convenient alternative term, and within the software domain it is inoffensive. So my project should be able to exclude it.

A project should be able to 'lock' their word list to a particular version of CLC. We don't want to be broken if CLC upgrades and adds words.

[julianhyde]

The existence of the config file would also be a convenient way for projects to 'opt in' to checking.