Changes to 1.0.4

* Add slope and vector field plotting, with a graphical solver for the
  slope fields.
* For graphing add SlopefieldPlot, VectorfieldPlot, SlopefieldDrawSolution,
  SlopefieldClearSolutions functions, and LinePlotDrawLegends,
  VectorfieldNormalized parameters.
* Add "Draw legends" checkbox to lineplots
* Add "Reset to original zoom" menuitem and add shortcuts for the zoom items
* Add Eigenvectors (only for 2x2 matrices), Parse, Evaluate, AskString functions
* Update the Mersenne prime list
* Clicking and not dragging on the plot now does a reasonable zoom-in
* Create plot window usable on my netbook
* Fix the compare functions and hence for loops starting at numbers less
  than 0.
* Fix the line plot scales
* Fix bug labeling line plot functions and several other minor bugs
  in the graphing code.
* Handle system errors (such as "out of file descriptors") more gracefully
* Minor other fixes and cleanup
* Translation updates (Hendrik Richter, Jesse Aviles, Djihed Afifi, Leonardo
  Ferreira Fontenelle, Fábio Nogueira, Koos, Jonh Wendell, Carlos Eduardo
  Santos, Jorge Gonzalez, Daniel Nylander, et moi)