* [updategraph] add support to use preset config instead of default minigraph * Fix variable case * Remove default minigraph case * Remove default minigraphs and add default_sku files
* Switch Vendor: Edge-core * Switch SKU: AS7312-54XS * ASIC Vendor: Broadcom * Swich ASIC: Tomahawk+ * Port Configuration: 48x25G + 6x100G * SONiC Image: SONiC-ONIE-Broadcom Signed-off-by: polly_hsu@edge-core.com