Refactor ActionTag...

... to accept either Unit or Service prefix.

Also NewActionTag() takes an actionId now
Rename HydrateActionTag to JoinActionTag
Merge pull request #12 from johnweldon/actiontag-refactor

Refactor ActionTag to accept more than just Unit prefixes
Make NetworkSnippet an exported constant.
Merge pull request #13 from tasdomas/network-regexp-public

Make NetworkSnippet an exported constant.
Update licence info to LPGLv3
Merge pull request #15 from wallyworld/fix-licences-1.20

Update licence info to LPGLv3
s/IsAction/IsValidAction/
s/IsEnvironment/IsValidEnvironment/
s/IsMachine/IsValidMachine/
unexport IsValidEnvironment
s/IsNetwork/IsValidNetwork/
unexport isRelation and rename.
s/IsService/IsValidService/
s/IsUnit/IsValidUnit/
s/IsUser/IsValidUser/
names: NewActionTag must panic if the action tag is not valid

The contract of the NewXXXTag methods is they should return a valid names.Tag impl or they should panic. As these functions are called almost exclusively in tests to create fixtures, this black and white pattern is appropriate.

This PR changes names.NewActionTag to the expected behavior and adds tests to assert this same.
typo
Merge pull request #16 from howbazaar/valid-names

Rename Is<thing> functions to IsValid<thing>
Merge pull request #17 from davecheney/108-new-action-tag-must-panic

names: NewActionTag must panic if the action tag is not valid