Simplified setup

I think I have found a way to make the lmfdb setup much simpler. But some testing would be welcome.

With this patch, on my machine, with a new sage-4.6 freshly downloaded, following the (updated) instructions, that is typing only
```
sage -i gap_packages
sage -i database_gap
sage -i pip
sage -b
sage -pip install -r requirements.txt
```
sets up everything so that all tests (but one on tensor products) pass.

two comments:
- first, I suspect that the problems with the Dirichlet characters on sage 6.4 are due to the fact that everyone
  uses an outdated package dirichlet-conrey. Jonathan and I have made changes in the Arizona workshop.
- this issue is solved here since I use pip to install all packages at once from requirements.txt, including the dirichlet_conrey module directly from Jonathan's github