Fix Item Editor GUI weirdness

Text fields (e.g. "Product Title"):

1. can't be right clicked on to show a popup menu unless you focus it first by left clicking.
2. when you focus a text field by left clicking, the caret is positioned at the start of the text field rather than where you clicked.
3. trying to drag to select text when the field is unfocused just positions the caret at the start of the text field rather than selecting text.

Numeric fields (e.g. "Cost"):

1. can't be right clicked on to show a popup menu unless you focus them first by left clicking.
2. dragging to select text when field is unfocused just selects all text instead of selecting the text you tried to drag.
3. uses the "arrow" cursor instead of "I-beam" cursor when mousing over.
4. text gets shifted when focusing the field.

eBay Categories dropdown:

1. sometimes clicking on the recent categories drop down arrow doesn't display the recent categories list e.g. if the window is unfocused and you click really fast or if you click, hold for awhile, then release.
2. clicking on the dropdown arrow doesn't dismiss the recent categories list, it just hides then displays it again.
3. SixBit doesn't recalculate text size when resizing the "eBay Categories" window. e.g.

a. if you have a really long title like "Main Category > Sub-Category #1 > Sub-Category #2 > Category" and shrink the window, SixBit will display the thing on the left "Main Category > Sub-Category #1" instead of the thing on the right "Sub-Category #2 > Category"
b. If you have a shortened title like "Sub-Category #2 > Category" and expand the the window, SixBit will still display "Sub-Category #2 > Category" instead of the full text "Main Category > Sub-Category #1 > Sub-Category #2 > Category"