Update fish to 2.7.1
Added cdh (change directory using recent history), argparse commands.
Array index errors are now silent.
String datatypes now support upper and lower subcommands.
Fish can now run commands before starting an interactive session. Use --init-command!
string escape has a new --stylexxx flag. Valid options are script, var or url.
Many small bug fixes + updated French/Chinese translations.
Added brand-new fish completions for grub, dhcpd, cdh, kdeconnect-cli, passwd, pip, snap and Sublime Text 3's Subl.
Lots of improvements to completions.
Test Plan: Install fish and use it as my default shell and test nothing seems broken.
Reviewers: Triage Team, DataDrake
Reviewed By: Triage Team, DataDrake
Differential Revision: https://dev.solus-project.com/D3376