Started my exposé on dg categories

Fixed all the mistakes with wrong paths, reinstated the use of
todonotes, added some macros, wrote down outline of my exposé and wrote
a first draft of an introduction
Wrote the first part on dg categories

And added the motivation from non-functoriality of cones
Wrote about the model category structures
Two new items in the bibliography

There are still plenty of them missing
Wrote about Toën's theorem, and the corollaries
Discussion of underlying and cohomology categories
Completed bibliography
Put the introduction in comments
Finished the first 7 sections

The first part is now a shortened version of the first chapter of my
thesis, containing only the necessary definitions.
Discussion of the dg nerve construction
Adding crucial proposition
Some small modifications
Nicer title for the work in progress

And better integration of my categorical notation with the convention
used in this text.
Discussed functoriality of dg nerve construction

And fixed 2 bad boxes, and a missing symbol
Discussed applications

And finished the bibliography, and fixed some mistakes.
Finished the notes
Fixed some typos
Added a proof, and fixed two small mistakes
Fixed character encoding issues in Higher stacks
Changed naming scheme of the files