Support for mechanical properties, better nested query support + GUI refactoring

The main goal of this merge was to add support for mechanical properties. This includes:

• Adding metadata and normalizer functionality for storing mechanical properties under results.properties.mechanical
• New GUI filters for bulk_modulus, shear_modulus and available mechanical_properties.
• GUI support for defining nested queries. The current mechanism works so that if you wrap input filter components within InputSection, they automatically become nested. Currently, only one nested query per section is supported, might change in the future. Also, there is not yet any syntax for defining nested properties through the search bar.
• GUI support for showing active nested properties. Added a new component for grouping FilterChips so that they differ from the "flat" filters.
• Support for the serialization of nested filter in the URL and in the API queries.
• Added GUI support for pressure units (needed for bulk/shear modulus).
• Normalizer + GUI tests

As a side effect, the following changes were made:

• The layout of property cards was simplified and unified. One no longer has to manually specify an aspect ratio and the layout is fully grid-based.
• Small restyling of the filter menus: Added vertical separators in order to better distinguish between different filters, especially important for the new nested filter sections.
• The new nested filters were enabled for band gap search (one task in #569 (closed)). This introduced a small rename for the metainfo related to band gaps.
• Restyling of the SectionTable component. Now looks like the default table from MUI.