Fix neuron mesh generation (from rebased branch)

[hanslovsky]

This is a summary of all the commits in #65 to avoid clutter in the commit history. The most important contribution is the replacement of the "flood fill" mesh generation by a mesh cache:

• render neurons based on selected ids, not based on mouse click location
• render neurons at all available mipmap scales
• segment mesh is set of meshes of contained fragments
• allows to track progress more intuitively
• three cache cascades (one cache per mipmap level):
  • block -> unique labels
  • id -> containing blocks
  • id, block -> mesh
• improve sources tab
  • split responsibility for displaying properties as nodes
  • be less ad-hoc, keep relevant state in separate classes
  • fix width glitches for mesh scale level sliders (hacky, for now)

I will not delete the original fix-neuron-mesh-generation
branch (for now) to keep the history.
Commit 1a8f926 is a summary of these commits in the
fix-neuron-mesh-generation
branch:

• 1ed6288 First cell cached mesh version!
• 4f943ab Remove System.out and commented code.
• 23971dd Remove more obsolete System.out logging
• 420809c Use meshes cache for integer labels also
• e214adc Run mesh generation in separate thread and multi-threaded
• 7d3d140 Remove obsolete line of code.
• cb9a4b6 Use only one stream and selected ids per source
• 78470db Introduce event-driven mesh rendering.
• 44fe3eb Invert normals
• 18eb6be Add specular reflections to meshes.
• aec4104 Explicitly set draw mode.
• a1aa615 Synchronized on meshes.
• cbc08dc Fix notification bug in SelectedIds
• d4e755a Add manual selection of ids via text field
• cf6d3d1 Add warning when blocklist cannot be found.
• 8c6ea33 Improve threading and naming of threads.
• 172aa9b Test to see if positinos cache works
• a5a2246 Run rendering in separate thread. ToDo: Make a single thread exectuor so every neuron only ever allocates one single thread
• 19ca24d Add first concept of cache loader cascades necessary for mesh generation
• 4aa728d Preliminary: Use new three-level cache for neuron retrieval.
• cbe9200 Do not remove neurons that are still selected.
• a095ba1 Improve naming and package structure
• c67a7c5 Identify meshes by fragment id, not segment id.
• 38377e8 Add convenience method to extract scale factors from source.
• 172619b Add some JavaDoc
• cd44808 Populate transform at scale level for correct scale factors.
• b3c3def Add more logging and set appropriate logging levels.
• 8e7f444 Set appropriate logging level
• 40722c6 Generate cascades of caches rather than CacheLoaders
• 577bf23 Add mock mesh simplification
• 93e0cf9 Add mesh simplification controls to UI
• cabff9c Add per id controls for mesh scale and simplification
• ba4f1b9 Remove obsolete slider for mock mesh simplifications
• aac04e0 Set number of decimal places to zero for integer slider/field
• 394e672 Remove obsolete class
• f5a5f42 Add progress tracker for mesh rendering
• 98b727b Fall back to version 8.40.14
• 38e54b3 Change behavior on non-finite values for status bar
• 6a2dd6f Do not bind to progress directly
• 33da7f4 Add convenience conversions between ARGBType and javafx Color
• e727b4e Add convenience methods for adding RandomAccessibleInterval
• 0c4c260 Throw exception when no volatile type matches
• 4b891a6 Fix bug
• 4b9fb43 Clean-up: Remove unused methods.
• 69dd161 Add logging
• 8b46eb1 Optimize merge fragments
• 368f5c6 Don't auto-populate fragment segment assignment
• 7c7fa67 Update SourceTabs