JTable: Fix absence of horizontal scrollbar and add popup menu actions

[tferr]

This ensures horizontal scrollbar is displayed when contents of table too small to fit in view port.
In addition, it implements a contextual menu hosting some basic actions:

• Copy and Select All command (from the JTable action map)
• Delete selected rows command
• Resize command that enlarges column widths to largest cell in the column

Fixes #62

[tferr]

@imagejan, @ctrueden, just to bump this. Is there anyone I can mention directly that would have the bandwidth to merge this? Tables remain quite unusable without it. I am happy to provide more details

[ctrueden]

@hinerm Do you have time to test and merge this PR? I wanted to do it today, but got sidetracked by scifio-labeling and ran out of time.

[imagejan]

Thanks @tferr for improving the table display!

When testing quickly, I observed inconsistent behavior before and after running the Resize Column Widths command:

• before: resizing the width of the window leads to appearance of scroll bar when the size gets too small
• after: resizing of the window is only possible down to the minimal column size; no scroll bar appears.

Here's a script I used for testing:

#@output a
#@output b
#@output c
#@output d
#@output e
#@output f
#@output g
#@output h
#@output i
#@output j
#@output k
#@output l
#@output m
#@output n
#@output o
#@output p
#@output q
#@output r
#@output s
#@output t
#@output u
#@output v
#@output w

a = 1
b = 1
c = 1
d = 1
e = 1
f = 1
g = 1
h = 1
i = 1
j = 1
k = 1
l = 1
m = 1
n = 1
o = 1
p = 1
q = 1
r = 1
s = 1
t = 1
u = 100000
v = 1
w = 1

This (minor) issue doesn't appear when the total width of the resized columns is larger than the minimal width possible for the window. (You can try for example by making the second column larger, like #@output m => #@output mmmmm.)

---

Anyhow, the suggested changes seem good to me, and an improvement to the current situation, so that minor issue shouldn't block merging this PR. 👍

[ctrueden]

👍 My only question is about the new public void removeRows(int[]) method. Is this an override or is it new public API? If new, we need to bump the major/minor version digit now.