Added environment variables that can be used during source package compilation to fetch package info (i.e $BPM_PKG_NAME or $BPM_PKG_VERSION)

Packages created using the -b flag will now contain the version number in their filename
Source install scripts will now exit if any error is encountered
Obsolete files should now be removed properly

test_packages/x86_64/bpm/pkg.info

@@ -1,6 +1,6 @@
 name: bpm
 description: The Bubble Package Manager
-version: 0.1.2
+version: 0.1.3
 url: https://gitlab.com/bubble-package-manager/bpm/
 license: GPL3
 architecture: x86_64