the LAYOUT option and minor modifications
improved abbrv for list; factorized code for toHTML(); reverted modifications to bib2html and created bib2links() instead.
changed the version number to __GITHUB__ (the github version is not a release)
fixed a spurious 'notice' when used as library
added a LAYOUT option

use @define(LAYOUT,{'table','list','deflist'}) to choose between table, ul, ol ('list' and ABBRV_TYPE='index') and definition lists for displaying bibtex entries.

$bib->index is now displayed as a number, not a number in brackets, for compatibility with list values. however this is invisible to the user because the brackets are added in getAbbrv().

bib2html now includes the echoing of links.
refactored the excellent commit of M. Guillaumin

- LAYOUT -> BIBTEXBROWSER_LAYOUT by convention
- BIBTEXBROWSER_LAYOUT has non-abbreviated values (for sake of intuitiveness)
- BIBTEXBROWSER_LAYOUT has no complex interplay with ABBRV_TYPE  (for sake of intuitiveness)
- ordered lists are responsible for the indices
- no new line at the end of the file
- renamed or moved some functions
merged with Martin's changes
merged with monperrus/bibtexbrowsed@17dbef223df40c11d536796d8d3c8453c045e9df. Simplified and improved the "keys" search option. Now uses a new ABBRV_TYPE option, prints a correct title, can read $_GET from the url. New function to sort by raw Abbrv.