Allow helm-projectile-ag to ignore

helm-projectile-ag now can also ignore files and directories based on
these variables:

- grep-find-ignored-files
- grep-find-ignored-directories
- projectile-globally-ignored-directories
- projectile-globally-ignored-files
Ignore files properly with helm-projectile-grep

Fix a bug where helm-projectile-grep does not retrieve ignore patterns
from relevant variables correctly. Now the ignored values are included
in the actual command.
Merge pull request #529 from tuhdo/master

[Bug fix] Use correct filter function
Merge pull request #522 from tuhdo/helm-projectile-search

Make helm-projectile-grep ignores files properly and allow helm-projectile-ag to ignore files/directories
don't advice functions defined in the same library
Merge pull request #534 from tarsius/no-advice

don't advice functions defined in the same library
[Fix #530] Change messages for consistency
[Fix #525] Change helm-projectile-sources-list order

- Prioritize file list above any other sources, except buffer since it is
usually small per project.

- Remove recentf list since it is just a subset of file list and if
  anything find-able in the recentf list, it should be inside file list.
  Remove to speed up helm-projectile command. User can invoke this command
  separately if they need a reminder of previously worked files.

- Remove directory listing for speeding up the command as well. Finding
  directory is a less frequent operation, and user can open a Dired
  buffer of the directory of current file anyway. This command has more
  meaning in stock Projectile then in Helm Projectile.

- Move project list to the bottom, since users won't need to switch
  project too frequently.
Merge pull request #533 from tuhdo/usability

[FIX #525 and  #530] Usability