Merge pull request #1074 from timmc/master

Bugfix: Restrict repo credential lookup to known keys.
credentials-fn != credentials
ensure only one set of quotes around java command in trampolines
use an appropriate location for system profiles on windows
move os detection into leiningen.core.utils
always process trampolines, even when used in aliases and higher-order tasks
remove unused leiningen.trampoline-file system property
Add :system to list of profiles applied by default.
Warn when system profiles contain :repositories.
Prefer ^:private to closing over an atom.

For consistency more than anything else.
Bootstrap leiningen-core with the base profile only.
Formatting for leiningen-core files.
Exclude in update-in task.
Formatting in tasks.
A few more news entries.
Move gpg setup notes from DEPLOY to GPG [fixes #1073]
Merge pull request #1077 from djpowell/windows-system-profile

use an appropriate location for system profiles on windows
Merge pull request #1078 from djpowell/more-bat-fixes

Support higher-order tasks and aliases that use trampolines in lein.bat
#949 Allow specification of artifact signing key.

Add :signing {:gpg-key "..."} option to project maps (global value)
and to :deploy-repositories maps (per-repo value). Does not yet work
in :repositories specs.

Also:
* Document per-repo :sign-releases option
* Delete unused defn deploy/signature-for
Remove outdated link to GitHub downloads page.
Tag tests which require network access.
Don't blow up when test eval-in-project doesn't return a number.

Hopefully only an issue when using :eval-in-leiningen.