Changes to 0.7.7 * Add IsPositiveDefinite, IsPositiveSemidefinite, QuarticFormula * SEMANTICS: QuadraticFormula, CubicFormula, Eigenvalues, and DiagonalOf now consistently return a column vector * Fix CubicFormula for complex coefficients and better handle real roots, and use QuarticFormula in PolynomialRoots * Eigenvalues now computes eigenvalues for 3x3 and 4x4 matrices * Add undo/redo capability * CHANGE: It's RayleighQuotient not RaleighQuotient * "Show Full Answer" menu item to show the full answer in a scrollable text window * "Next/Previous Tab" menu items and accelerators, also Programs menu now always displayed and has a "Console" menuitem too. * Mixed fractions can now be set in the preference box * The preference box has options for remembering (or forgetting) the output/precision settings. Normally these settings are probably temporary and hence we don't want to remember them always. * Preference box has "Help" button * When graphing a surface when we encounter complex value or other errors, don't assume 0, but just don't graph anything at that point. * Cosmetic changes to UI * Documentation updates * Fix plugin reading * Portability fixes * Translation updates (Pema Geyleg, David Lodge, Francisco Javier F. Serrador, Djihed Afifi, Pawan Chitrakar, et moi)