Migrate tables from imagej-common

[imagejan]

This PR migrates the classes in the net.imagej.table package from imagej-common into the org.scijava.table package of this repository, keeping their git commit history.

The ImageJ-specific classes (that had references to Img) were removed. ResultsTable will be replaced by DoubleTable in another commit, and an ImageJ-specific implementation of ResultsTable can remain in imagej-common.

This PR supersedes #1 that didn't contain the git history of the affected files.

[imagejan]

@ctrueden please let me know if you're fine with this.

My next steps would be:

• [x] Add DoubleTable class in line with other *Table classes to replace former ResultsTable (see https://github.com/scijava/scijava-table/commit/8ae71d64c0ae1c757c3a820504a2b49bfec540c6)
• [x] Deprecate classes in the net.imagej.table package of imagej-common that have a replacement here (see https://github.com/imagej/imagej-common/pull/78)
• [x] Migrate imagej-plugins-io-table to scijava-plugins-io-table (see https://github.com/scijava/scijava-common/issues/314#issuecomment-366215790)
• [ ] Update other projects using these classes (in particular imagej-legacy and imagej-omero)