Use projectile-commander and bind it to `<SPC> p p`
Fix ido-vertical key bindings stability

Sometimes the spacemacs key bindings for ido-vertical did not work.
`fd` can exit help window
Fixes #51 Projectile cache remains empty

I had to explicitly enable projectile-enable-caching and explicitly
start projectile-mode to initialize projectile-projects-cache
Simplify binding for projectile-commander to <SPC> p

Also add ?r projectile-replace to commander
Update projectile documentation in readme
Remove ?r command for projectile-commander

It is now part of the package
Change projectile commander command ?F to ?h

This is the command for helm-projectile
Added guide-key to help find SPC mappings