Update packaging to conform with package unification and few fixes (#372)

* Rename package (dupeguru-se -> dupeguru)
* Update package name in .desktop files and scripts
* Add Ubuntu package building instructions
* Fix build_pe_modules.py
* Add description to package
* Add conflicts dependencies to replace previous versions
* Update python version
* Unify .json configs
* Few cosmetics changes (mainly missing end-lines and images permissions)

pkg/arch/dupeguru.json

@@ -0,0 +1,7 @@
+{
+	"pkgname": "dupeguru",
+	"longname": "dupeGuru",
+	"execname": "dupeguru",
+	"arch": "any",
+	"iconpath": "/usr/share/dupeguru/dgse_logo_128.png"
+}

pkg/arch/me.json

@@ -1,7 +0,0 @@
-{
-	"pkgname": "dupeguru-me",
-	"longname": "dupeGuru Music Edition",
-	"execname": "dupeguru-me",
-	"arch": "all",
-	"iconpath": "/usr/share/dupeguru-me/dgme_logo_128.png"
-}

pkg/arch/pe.json

@@ -1,7 +0,0 @@
-{
-	"pkgname": "dupeguru-pe",
-	"longname": "dupeGuru Picture Edition",
-	"execname": "dupeguru-pe",
-	"arch": "any",
-	"iconpath": "/usr/share/dupeguru-pe/dgpe_logo_128.png"
-}

pkg/arch/se.json

@@ -1,7 +0,0 @@
-{
-	"pkgname": "dupeguru-se",
-	"longname": "dupeGuru",
-	"execname": "dupeguru-se",
-	"arch": "all",
-	"iconpath": "/usr/share/dupeguru-se/dgse_logo_128.png"
-}