Allow manual installation of the kernel

[quantum-byte]

Hi,

with multiple different environments one can currently only use one because the kernel name is always "ipyflow". So jupyter will only pick up the first in its search path.

It would be quite helpful if one could use ipyflow.install to manually install the ipyflow kernel with different names like ipykernel install allows via --name and --display-name variables.

Then one can specify different names for different environments and jupyter will pick them all up.

Additionally the kernel resources are only available during the package installation. One still can use ipyflow.install afterwards, but there will be no icons for the kernel.