add support for data installations

[smoors]

motivation

• leverage EB to install data in a standardized way with proper versioning and checksumming
• support adding datasets as dependency for software
• easily swap dataset versions with ml swap

changes

• add cmd line option --installpath-data similar to --installpath-software
• add cmd line option --subdir-data (default = data) similar to --subdir-software
• add cmd line option --sourcepath-data similar to --sourcepath
• add Easyconfig parameter data_sources similar to sources

design

• the main reason for a separate subdir_data is reusability: in contrast to software it does not have to be rebuilt/reinstalled when for example upgrading the OS or building for a new architecture
• the reason for a separate sourcepath_data is that datasets can be very large, so you may want to store them in a different file system or location.

[Micket]

Tests needs adjusting
test_prefix_option:

easybuild-framework/test/framework/options.py

Line 5032 in 92d2968

def test_prefix_option(self):

test_show_config:

easybuild-framework/test/framework/options.py

Line 4886 in 92d2968

def test_show_config(self):

[boegel]

@smoors Let's re-target this to 5.0.x / EasyBuild 5.0, not because it involves breaking changes, but because it can serve as a "flagship" feature of EasyBuild 5.0 (seems a bit too much to introduce in a 4.9.x bug fix release)?

[boegel]

@smoors I changed to target branch in this PR from 5.0.x to develop, you should synchronize your PR branch with current develop branch (which has received a massive update after the release of EasyBuild v5.0.0, see #4825)

requested changes done

[branfosj]

I'm happy with this. The changes are all to maintain alphabetical order.