<feat>(first aliases) Adding firsts aliases

Add aliases :
- checkout : co
- commit : ct
- push : ps
- diff : df
- branch : br
- pull : pl
<fix>(reversing alias declaration)
<fix>(change mail gitconfig)
<feat>(gitignore + other aliases in gitconfig) Adding gitignore and some aliases in gitconfig
<feat>(others aliases) dfc : diff --cached, unadd : reset HEAD