"install" target for luna

-Installs in /usr/bin if run by root, else ~/bin
Fix build on cygwin

-Remove unnecessary error message about cygwin1.dll
-Add necessary flags to luna's Makefile
Revert "luna: add support for .BMP resources"

The changes on luna broke ndless_installer.tns
Add nspire-tools path command

-Returns absolute path to the ndless sdk
Fix Makefile.tpl

-$(DESTDIR) used together with vpath
Newer version of nspireio
Add support for --gc-sections