Add support for seperate consumption/production entities and a few layout and copy tweaks.

[raldred]

Thank you for creating this wonderful card. I have made a few changes which I'm using myself, I wondered if any of these may be useful to the main branch.

• Added support for separate consumption and production entities for flows. Adds flexibility and simplifies use by users of lxp-bridge (maintains support for multiple inverters)
• Fixed the header not settable, renamed to title for consistency with other HA cards.
• Shows full battery image if SOC >= 99 (Some inverters never return SOC at 100%)
• Reworked the arrows and adjust the css grid to help with consistent spacing and sizing
• A few label and icon adjustments to align more with current Lux UI

I've split them up here into separate commits here, but I'd be happy to split them into separate PRs if you'd be interesting in merging any or all.

example separate entity config:

grid_flow:
  entities:
    - consumption: sensor.lux_power_from_grid_live
      production: sensor.lux_power_to_grid_live