Scipion-app

- Adapted to variables registry
- printenv refactored (does not print export) and is more detailed.
- Replace pip internal command with subprocess call

users:
- Adapted to sprites
- Defining TomoDataViewer as the TiltSeries default viewer

developers:
- Exist code is not masked when running xmipp, relion etc commands
- CommandDef and CondaCommandDef assist in the definition of commands for the binaries

- Update message is green now
- SCIPION_DONT_INSTALL_BINARIES is used in the plugin manager to initialize "Skip binaries" check box
- Do not raise error when one of the CUDA env vars is not set

users:
- Fixing an error related with the Plugin Manager when clicking the plugin treeview
- Fix workflow tutorial intro.
- New variable (flag) to define if binaries are installed by default or not --> SCIPION_DONT_INSTALL_BINARIES (any value will deactivate installation of binaries
- scipion3 config -p <relion> (or any other): shows plugin url too
- SetOfVolumes and SetOfParticles have DataViewer as the default one.

developers:
Update the methods checkLib and addPackage to improve the installation of plugins with libraries dependencies.

users:
old config file is now backed up (at backup/scipion.conf.YYmmDDHHMMSS) always after any scipion config command that updates the config files.

developers:
protocol.conf is not handled anymore in the config.
tar files are allowed.
compressed file without a "folder inside" should also work.