Fixed the default package version for pacman to '';
Pacman does have packages of the form php{version}-{extension}. so i
chanded the default version of pacman to php-{extension}

NB: This occurs only when the packageManager used is pacman.

…e is missing

Sometimes, valet install/uninstall will throw some file not found errors
when you try installing valet in computer with no previous config files
or config file absent

… inexistent old path

If u tried installing nginx in a situation where ~/.config/valet/Nginx
doesn't exist, it'll throw a warning saying the path/file (previous
configured) doesn't exist

With the previous changes made the prevents valet from getting configs
from inexitent config files, i had the add a default custom domain while
resecuring nginx configs

from the list of php extensions required by php-fpm, the only one
installable on its own is php-gd (pacman package managers). I made sure
to ignore the orders which caused an issue while downloading extensions.
The others come with php by default

…ig file doesn't exist

Sometimes, valet's config file may be missing and will be suitable to
add a default domain ('test') in case the config domain doesn't exists

…inx configs

…compatibility

Recent versions of ```ca-certificates``` are installed in
```/usr/share/ca-certificates``` whereas the path specified in valet is
```/usr/local/share/ca-certificates```. the previous path wasn't
removed. but a check is done first to check if prevoious path exists
before using recent path

…rsioned packages

I create a new method on the PackageManager Contract which determines if
a given package manager supports package versionning and implemented the
method on all Package managers.