!! Give future long- and short-term developments

Short-term:
0) finish MANUAL
1) cleans the test suite in gen1int_host.F90
2) tests Cartesian/spherical multipole moment integrals
3) tests the calculations of expectation values; why calling PR1IN1
   with expectation values returned gives wrong results
4) enables London atomic orbitals
5) uses header files in Gen1Int library?

Long-term:
1) adds functionality of reading/writing integrals and/or expectation values on file
2) considers molecular symmetry
3) works together with other modules, such as geometry optimization and response
   theory calculations
