[Blu Pure XL] Short Circuit:
This is for those of you who want to have softkeys on your Pure XL and don't mind losing the screen estate (and some tinier UI) in order to gain it

Requirements:

You must be Rooted

Custom Recovery (I'm (still) on TWRP 2.8.6.0 by [MENTION=1735457]acheron1502[/MENTION])

Root Explorer (or similar application; BLU's File Explorer app doesn't browse to root afaik)

MicroSD card or USB stick and OTG cable

Text Editor (or your root explorer app's text editor)

I understand that there are other (easier) ways to enable softkeys, but I will only be going over the method I used here (through manual editing of the build.prop).

In Android System:

Navigate to /system in your root file explorer application

Copy build.prop onto your microSD card or USB stick

If you used a USB stick, remove the USB and plug it into your computer

If you used your microSD card in the phone, plug your phone into your computer

If you can't access your microSD card through your phone on your computer, go back on your phone, drop down the notifications bar and tap Connected to a USB or Connected as a camera, and tap the File Transfer box on the UI that appears on the bottom of your screen

Open build.prop with your text editor from your USB stick or microSD card on your phone (In my case, I was on Windows and I had Notepad++ installed, so I used that)

Change this line of code in build.prop

qemu.hw.mainkeys=1

to

qemu.hw.mainkeys=0

OR

You can also choose to modify this section of code

# temporary enables NAV bar (soft keys)
#Gionee lihf 2015-01-26 remove for navbar
#qemu.hw.mainkeys=0

by removing the # in front of this line ONLY

#qemu.hw.mainkeys=0

Save the build.prop after you've made that change and reboot your phone into custom recovery

In Custom Recovery:

Plug in your OTG cable with your USB stick plugged in (if you used your USB stick)

Mount your system partition (and USB, if you used that) by tapping Mount > System (and USB Storage) so that the box(es) have an X in them

Go back to the main screen, tap Advanced > File Manager and navigate to /system

Tap build.prop > Delete and swipe the bar right, then tap Back

Navigate to your USB (/usbstorage) or microSD card (/external_sd)

Tap build.prop > Copy File, then navigate to /system and tap Select on the bottom right of your screen. Swipe the bar to the right to confirm

IMPORTANT:

Before you reboot into Android, you must navigate back to /system and tap build.prop > chmod > Type in 0644 instead of 0000 > Go (on the bottom right)

Swipe the bar right to confirm and tap Done. NOW you can reboot back into your Android system. (You don't need to clear dalvik/cache for this)

Failure to do so will result in your phone not being able to boot

When you unlock your phone, you'll have softkeys on the bottom of the screen (along with functioning hardkeys as well)!

I'm not sure if it's possible to switch the positions of the recent apps key and the back key (if you prefer the back key on the right)

There is no option to turn softkeys on/off in Settings>Advanced settings>Developer options, so if you want to undo this, you'll have to change qemu.hw.mainkeys=0 back to 1, replace build.prop, set permissions, and reboot again.

DISCLAIMER:

I'm not responsible if you brick your phone somehow by not following the instructions. I've tried to make it as clear as possible.