Black box version 1.15

Changes since 1.14
- Bug fix in sat.Or
- Massive overhaul of BackSearcher.java and all of the children of History.java
  - Fixes some major bugs in sequence generation
- Bug fix: Editing a response works now

Changes since 1.13
- "Clear All Rows" button is gone
- Clicking "X" gets intercepted

Changes since 1.12
- Tied together the close buttom and the Exit menu option

Changes since 1.11
- Fixed up findError() (very buggy previously)
- Impossible histories that are edited into error will now keep the original
  non-error history
- Stimuli used _only_ in impossible histories may no longer be deleted

Changes since 1.10
- Fixed bug with "only":
  - NullPointerException got thrown when analyzing histories using "only"
  - This was a general failure to assign a BlackBox to a History when the
    History was generated outside HistoryParser
  - The entire class hierarchy was restructured to prevent this from ever
    happening, by requiring every History to have a BlackBox via the
    constructor
- Fixed error messages
  - Previously, error messages could be "embedded" in a History
  - They are now extracted

Changes since 1.09
- Added "only" and "oneof" keywords
- Fixed "embedded error message in table" bug
- Fixed Macro generator bug:
  - When generating, the generator always starts with the same sequence 
    every time the button is clicked

Changes since 1.08
- Bug fixed in BackSearcher.java

Changes since 1.07:
- When a stimulus or response is renamed, the renaming now gets propagated
  through all of the history set specifications.  Previously, this did not 
  happen, rendering some of these specifications illegal due to the presence
  of the old name.
- The completeness checker did not take "impossible" sequences into account.
  This has been fixed.
- The generator generated all _legal_ sequences it found, regardless of whether
  they matched the target history.  This has now been fixed by adding a call
  to matches() before adding a sequence to the generated list.
  
Changes since 1.06:
- ConcurrentModificationException in CompareHistory fixed
- Macro editor closes when a change is registered

Changes since 1.05:
- Disabled "redo" menu item; it is buggy and needs some attention
- The stimulus/response editor
  - Closes automatically when changes are made
  - Restores name and description when erroneous values are entered
- The completeness checker:
  - Major bug fix in StimulusSeq.isValidUsing()
  - Sequences ending in a row outside the black box are still technically
    valid; this has been changed to require a legal row number
- Editing while searching:
  - Previously, if a black box is edited while a search is in progress, 
    the search may crash and prevent further searches from being launched
  - Now, an edit to a black box while a search is in progress terminates
    the search

Changes since 1.0:
- Fixed bug in BackMoves by adding "strongly preferred" stimuli
- Changed all fonts to courier for user-entered information
- Got rid of debugging output
- Fixed up the help options a bit
