Added XLSX btn title

See merge request !830

Features/display semester data

See merge request !828

Features/new half year feedback form

See merge request !827

Features/default EmailTemplate for HalfYearProcess and HalfYearProcessOverdue

See merge request !826

Added waive to volunteer xlsx

See merge request !825

feat(semester-process-volunteer): add nested attribute form table to select volunteers for semester-process

- in order to have elegible volunteers to be rebuilt for the changed semester daterange

feat(semester-process-volunteer): add controller, routes, policies and basic scaffold for views to the model

Feat/semester process volunteers initial builders before creation

Closes #459

See merge request !823

- takes query of elegible volunteers and then builds SemesterProcessVolunteer for each
- if array of volunteer ids is passed, it will only build SemesterProcessVolunteer for these

- if passed from form input, it can build the correct semester that was passed from form input

- so that it can be treated as a child of this in forms
-

- relations to all hours with meeting date within the semester
- scaffold empty semesterFeedback record for each mission related
- build the SemesterProcessMail.kind == :mail for the initial mail

feat(semester-process-volunteer): builder that assigns the elegible missions from the volunteer to the SemesterProcessVolunteerMission join table relation