Improve search

[rinigus]

From #7 (comment) by @Olf0:

• IMO it is fine that the search is case-insensitive, but it also does not search for "words" (e.g., in contrast to Openrepos). I.e., any string match results in a hit, which is confusing simple users: E.g. searching for "Imp" would match "simple" (confusing) and "Imperial" (fine IMO). Hence you may want to match strings only on the start of a word, with words being delimited by any non-minor letter (![a-z]) character (by white-spaces, numbers and non-letters to the left and right, by capital letters [A-Z] only to the left), but any non-whitespace character in the search string must be evaluated; i.e. searching for "go" shall match "SailGo", "game-go" and "coffee2go", but not "Farango".
• Alternatively to the point before: Being able to limit the search solely to package "pretty names" (because e.g., searching for "Go" (the game) basically fails, because of hundreds of unrelated hits) may also alleviate this issue, but means another pulley entry, another way of user interaction etc.; IMO this would be an inferior solution, because optimally a search functions simply finds the right stuff, but not (much) more than that.