[ENH] Steel sections improvements

**Is your feature request related to a problem? Please describe.**
There are some improvements I'd like for the steel section module

**Describe the solution you'd like**
- [x] Names should be consistent with eurocode, e.g.
```
h,b,t_w,t_f,r,m,P,A,A_vz,A_vy,I_y,i_y,W_ely,W_ply,I_z,i_z,W_elz,W_plz,IT,WT,I_w,W_w
```
- [ ] Dataclasses should have unit types
- [x] Find a cleaner solution for the _PROPERTY_NAME_MAP dictionary
- [x] Make `_import_section_database` a public function
- [ ] Add an input flag to `get` or restructure the code to allow a user to create a section by providing just the row from the database as input: This is useful when the use wants to inspect, compare or manipulate the values in the section dataframe before choose a section - it also improves code performance by not requireing the reloading of the database when the user wants to iterate through many different sections
- [ ] Include option to return the whole database as list of sections
- [ ] Include an option to return the section with floats instead of the units -- useful for people who want to use the section database outside of our EC design framework