Add Project.toml, speedup of isregistered and getkey, path consistency

[hhaensel]

During my work at JuliaGizmos/WebIO.jl#417, I realised some (minor) performance issues with getkey(), which I thought was due to the recalculation of the key.

Only later I realised that the main bottle neck - at least on my windows machine - is from abspath(). Nevertheless, I propose a PR here to change getkey such that it checks for the values of the registry instead of the keys, and at the same time bring AssetRegistry to the new package format.

[twavv]

It's been a minute since you made this PR (sorry!). Are you still interested in having it merged?

I don't understand why this change is being made. Why would we prefer ... in values(...) over haskey?

[hhaensel]

It took some time for me to remember 😉
First of all, it is not a very important point, as abspath() is taking most of the time.

haskey() is not the point but the calculation of sha1, everytime that you call getkey(). If the paths are long you might gain some speed in searching for the keys instead of the values. But the potential gain in speed is probably not worth the complication in code.

I think the most important about this PR in the end is the usage of normpath(). It will get rid of . and .. which caused trouble for me, if I remember correctly.

So why not making the following change?

- getkey(path) =  baseurl[] * "/assetserver/" * bytes2hex(sha1(abspath(path))) * "-" * basename(path)
+ getkey(path) =  baseurl[] * "/assetserver/" * bytes2hex(sha1(normpath(abspath(path)))) * "-" * basename(path)