install: rewrite install script

* set dependency versions: PPA, git repository & commit
* separate download and build+install steps
* don't reinstall package if it's already installed

refs #4630

Change-Id: I966fac5e1633cbabf78ce20cd151a35618efc345
diff --git a/.gitignore b/.gitignore
index a02d875..ee70e67 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,10 +11,8 @@
 
 # Misc
 .DS_Store
-mininet
-mn_wifi
-ndn-src
-openflow
+dl
+*.apconf
 
 # Vagrant
 .vagrant