REL: bump version to 0.7.0

REL: bump version to 0.6.0

Merge pull request odlgroup#826 from odlgroup/issue-822__ray_trafo_im…

…pl_default

Issue 822  ray trafo impl default

Merge pull request odlgroup#696 from odlgroup/update_install_doc

Update install doc

REL: update release date of 0.5.1

Merge pull request odlgroup#654 from odlgroup/release_note_updates_fo…

…r_0.5

DOC/REL: Update release notes with several PRs for 0.5

Merge pull request odlgroup#504 from odlgroup/odl040

REL: create 0.4.0 release notes

REL: bump version to 0.3.1

Merge pull request odlgroup#441 from odlgroup/issue-336__move_odlpp

Issue 336  move odlpp

Merge pull request odlgroup#469 from odlgroup/issue-463__phantoms_folder

API: move phantoms to new odl.phantoms dir