Parsing profile with 15 minute timestepping

[tolga-akan]

Currently timestepping is by default 1 hour.
The goal is to support also 15min timesteps in the data, but only if the data is also required with 15minute timesteps.

• Updated/check profile parsing such that it parses 15min data as 15minute.
• Updated/check profile averaging for x hours/days are taking accordingly when bigger timesteps are requested.
• Add test that checks the profile parsing for 15min timesteps and that the right amount of variable with correct timesteps are created
• Create a test where the optimization is tested with 15min timesteps and check that there are no other strange things happening with indexing. This test should not happen with the grow workflow, but should be on a test problem and should also include a producer and electricity profile.

[tolga-akan]

@FJanssen-TNO @KobusVanRooyen Ready for reviewing