Don’t pre-select (find) “in selection” by default

Previously this would be selected if the user had a multi-line selection and was pressing ⌘F. The old behavior can be restored using:

    defaults write findInSelectionByDefault -bool YES
Don’t let up/down abort multiple carets when all on same line

In this situation, abort the multiple carets by moving them all to the beginning or end of the current line (⌘←/⌘→ or ⌃A/⌃E).
Ensure tab size read from .tm_properties is larger than zero

Closes #1028.