Project creator 2.0

[K-Meech]

Main changes:

• adds correct downsampling for segmentations
• splits export functionality from ExportImagePlusAsN5Plugin into a separate class: WriteImagePlusToN5
• removes hdf5 support
• changes default compression to gzip
• larger string fields in project creator
• Splits project creation into choosing a project name + project folder
• handles spaces in filepath
• refactored into more classes
• various small fixes

Still WIP:

• adding remote metadata

[K-Meech]

Alright - I think this is ready to merge now!
In addition to changes above, it adds:

• command for writing remote metadata to a project

@tischi - I changed XmlIoN5S3ImageLoader a bit, as the current toXml() wasn't giving the correct formatting

[tischi]

I will merge it, but could you please locally first check whether it merges well with the current master from today (because I just merged changes from @constantinpape and maybe there could be conflicts...)

[K-Meech]

I just checked - and all looks good!
I already made some changes to fit with @constantinpape (i.e. removing all the authentication fields)

[tischi]

You guys are faster then ⚡

[tischi]

Why is this PR still open? It is merged, isn't it?

[K-Meech]

It's merged! - but there's an old one: #184 that still needs to be closed